ABSTRACT
Many pharmacological proteins or peptides require to be intracellularly delivered to target and modulate cellular functions at the subcellular levels. A huge body of information about cellular metabolic and signaling pathways essential for tumorogenesis and tumor cell development allows for the identification of proper targets for interference with the tumor growth. Although peptide inhibitors, discovered through the use of phage-display or combinatorial peptide libraries had excellent in vitro activity, they were not considered for drug development because of poor pharmacokinetics and their inability to reach the molecular targets inside the cells. Intracellular transport of biologically active molecules with therapeutic properties is one of the key problems in drug delivery in general. Cell Penetrating Peptides (CPPs) are a group of peptides, usually containing a cluster of basic residues that have been recognized as promising drug delivery vectors over the last decade.
